The invention pertains to a sieve for a harvester thresher which consists of a frame and adjustable louvers that are mounted therein and can be adjusted by means of a motor-driven adjusting drive. The sieve comprises at least two sieve elements that are arranged in a common plane and are respectively provided with a frame.
Typically, in a harvester thresher, also known as a combine, after threshing and separation, some chaff and straw are still mixed with the grain. The cleaning unit removes this trash from the grain. In most combines, the cleaning unit comprises three major components: a cleaning fan, an upper sieve and a lower sieve. Sometimes the upper sieve is referred to as a chaffer. The upper and lower sieves are generally similar in construction, although the components may differ in size. The cleaning fan has its own housing, whereas the sieves are mounted to the cleaning shoe.
The sieves are suspended on hangers attached to the sides of the cleaning shoe. The sieves are either adjustable or non-adjustable. The adjustable sieve is made up of a series of transversely extending louvers with rows of teeth. Each of these louvers is mounted on a crankshaft having a crank arm that engages an axially extending adjusting bar. By axially moving the adjusting bar, all of the louvers are moved simultaneously.
It is known from DE 71 45 564 U, EP 1 068 792 A and EP 1 068 793 A to provide the frame of a sieve that forms part of the cleaning device of a harvester thresher with an electromotive adjusting drive in order to adjust the width of the sieve openings. In order to prevent the play created between the adjusting drive and the louvers of the sieve by intermediate transmission mechanisms in the form of Bowden cables or the like, the adjusting drive is arranged on the sieve frame.
When adjusting the sieve in accordance with EP 1 068 792 A, two sieve elements of the upper sieve, which are arranged laterally and adjacent to one another, are adjusted by a common adjusting drive. A connecting rod or a threaded spindle is arranged for this purpose between the sieve elements and transmits the driving motion of the adjusting drive from one sieve element to the other sieve element.
In this case, it is disadvantageous for the connecting rod or the threaded spindle to have a certain amount of play resulting from inaccurate adjustments of the louvers in at least one sieve element. In addition, the connecting rod must be detached and subsequently reattached when one of the sieve elements is removed for maintenance or repair purposes.
The invention is based on the objective of additionally developing a sieve for a harvester thresher which is composed of several sieve elements in such a way that a more precise adjustment of the louvers can be achieved.
In a sieve for a harvester thresher which is composed of two sieve elements that lie in the same plane, the invention proposes to assign a separate adjusting drive to each sieve element. If more than two sieve elements are provided, each of the sieve elements can be provided with a separate adjusting drive. However, it would also be conceivable to provide a first sieve element with a first adjusting drive, and to provide two or more additional sieve elements with a second, common adjusting drive.
In this way, the sieve elements can be adjusted with less play (free travel and hysteresis) and even independently of each another. When removing the sieve elements from the cleaning shoe for reasons of maintenance, cleaning or repair, it is no longer necessary to separate and reconnect the drive connection between the adjusting device and the adjacent sieve element, which is time-consuming.
The reduced surface of the louvers that is assigned to an adjusting drive makes it possible to use smaller and therefore less expensive adjusting drives. Due to their low weight, they can be directly mounted on or in the frame of the sieve element.
The sieve elements are arranged in one plane and are usually situated laterally adjacent to one another relative to the forward driving direction of the harvester thresher. However, it would also be conceivable to arrange the sieve elements one behind the other. Sieves that are composed of multiple sieve elements may be considered for lower sieves as well as upper sieves.
The adjusting drives may contain electric, hydraulic or pneumatic motors for generating a linear or rotational movement. The motors are provided with connecting elements for coupling to the power supply. The connecting elements are preferably automatically disconnected from connections that are arranged in and remain in the cleaning shoe when the sieve elements are removed, and automatically connected thereto when the sieve elements are installed. This significantly simplifies and accelerates the removal and installation of the sieve elements.
A sieve according to the invention for a harvester thresher makes it possible to adjust the louvers of the sieve elements separately, as well as to realize different adjustments of the louvers of the sieve elements, by means of a corresponding manual or automatic control. Different adjustments make sense when the harvester thresher is used on hills, where it is advantageous to close the uphill sieve element further than the downhill sieve element. In this way, the air current generated by the cleaning blower is forced to flow more intensely through the downhill sieve in order better to penetrate the layer that is naturally thicker on the downhill side. A separation of undesirable non-grain constituents is simultaneously prevented in the thinner layer on the uphill sieve. This results in an improved efficiency of the harvester thresher on hills.
According to another embodiment, the sieve elements may also be controlled as a function of the signals from sensors that are assigned to the sieve elements. Sensors of this type are able to sense the separation of grain or non-grain constituents underneath the sieve elements. Their signals are fed to a suitable control or regulating device that controls the adjusting drives of the sieve elements in such a way that separation and purity are optimized for each sieve element. This can be further simplified by utilizing more adjusting drives or separately adjustable sieve elements.
Two embodiments of the invention are illustrated in the figures and described in greater detail below.